Method and device for the automatic control of illumination devices

ABSTRACT

A method and a device are proposed for the automatic control of illumination devices ( 24 ), having a control element ( 22 ) which acts on illumination devices ( 24 ) and which is calibrated at time intervals (T), for which various calibration parameters are taken into account.

BACKGROUND INFORMATION

The present invention relates to a method and a device for the automatic control of illumination devices, particularly of a motor vehicle, according to the species defined in the independent claims. Such methods are already known—for example, from the German Patent 195 23 262—but they describe only how the external illumination devices are controllable on the basis of an absolutely incident quantity of light. However, an unwanted change in the control characteristic results due to various aging effects.

SUMMARY OF THE INVENTION

The method of the present invention having the features of the main claim has the advantage that the control element, which acts on the illumination devices, is calibrated at time intervals, thereby permitting compensation for aging effects of the optical media situated in the sensing region.

A further advantage is yielded if the calibration parameters of a rain sensor, which is likewise calibrated at time intervals, are relayed to the control element. The rain sensor and the control element for controlling illumination devices are frequently arranged in a single housing and have similar or even identical optical media. The result is that the aging process of both optical media proceeds in a similar or really identical manner.

The measures specified in the dependent claims yield advantageous further developments and improvements of the features indicated in the main claim.

It is advantageous if the rain sensor has a transmitter, a receiver and a light-conducting member; the receiver receives the light conducted through the light-conducting member from the transmitter and compares this signal to a setpoint value. In this way, the transmission properties are easily ascertainable, which means a simple calibration of the control element may be carried out.

A higher accuracy may be achieved if a transmittance is determined as result from the comparison of the received light signal to the setpoint value, and the control element is calibrated with the aid of this transmittance, since it is substantially responsible for the shift of the operating point of the control element.

If the control element has a second light-conducting member which is in correlation with the optical properties of the first light-conducting member, then this correlation may be taken into account in the calibration of the control element. In this way, the light-conducting member of the control element may be different from the light-conducting member of the rain-sensor device, in particular may be made of various plastics or glasses. Due to the correlation of the optical properties, the control element may still be calibrated exactly.

If the correlation is stored as a functional cohesion in the control element, any correlation as desired of the optical properties of the two light-conducting members may advantageously be taken into account in the calibration, provided they are able to be represented functionally.

If the calibration is carried out with the aid of a correlation stored as a table in the control element, storage and computing power of the control element are minimized. The calibration can then be carried out in a very simple manner without having to forfeit some of the flexibility of the correlation.

In addition, it is particularly advantageous to provide a calibration section over which a calibration parameter, which is taken into account during the calibration, is determined at time intervals (I).

A very simple calibration may also advantageously be performed, in that it is only carried out as a function of time. Particularly in the case of plastics, it is possible to proceed in this manner as a rough approximation of the transmission change, which means no further measuring distances are necessary.

A further beneficial calibration possibility is given if the calibration is a function of the brightnesses measured during the history of the control element. The optical properties of many plastics change as a function of time and the intensity of the light to which the plastics are exposed. If these variables are measured, with the aid of empirical values, it is possible to draw conclusions about the optical properties of the plastic.

Moreover, it is advantageous to in each case construct the light-conducting members and the electronics of the rain sensor and the control element in one piece in order to save installation space and reduce costs.

The device of the present invention having the features of claim 10 has the advantage that the control element is calibrated at time intervals. It is thereby possible to compensate for aging effects of the optical media, situated in the sensing region, or of the receivers. In this context, it is particularly advantageous if the calibration parameters of a rain sensor are usable for calibrating the control element.

It is particularly advantageous if the rain sensor has a transmitter, a receiver and a light-conducting member, and the receiver receives the light conducted from the transmitter through the light-conducting member, to in this way emit transmission-dependent signals. Transmission properties are ascertained in this manner, thereby allowing a calibration of the control element. If, moreover, the control element has a second light-conducting member whose optical properties are in correlation with the light-conducting member of the rain sensor, a simple and nevertheless precise calibration of the device advantageously results.

Due to the storage of the correlation in the control element as a functional cohesion, it is possible to store every correlation of the optical properties of the two subassemblies, rain sensor and control element, representable as function.

The correlation is advantageously also stored in the control element as a cohesion in table form, in order to permit a rapid calibration using as little computing expenditure as possible.

If the two light conductors of the rain sensor and of the control element are constructed in one piece, then a similar change in the optical properties results, since both are subject to the same exposure of sunlight. This is advantageous since the transmission properties of plastics are influenced substantially by the ultraviolet radiation to which they are subject during exposure to sunlight.

In addition, arranging the electronics of the control element and the electronics of the rain sensor in one piece on a single printed-circuit board saves costs and resources.

It is also advantageous if the control element is able to be calibrated at time intervals using a calibration parameter which is a function of the service life of the control element. Aging effects of the optical media, or even aging effects of the receiver elements, which typically are constructed as semiconductor components, are to a high degree time-dependent, which means the calibration on the basis of the service life represents a good first approximation.

It is also particularly advantageous to be able to calibrate the control element with the aid of a calibration parameter which is a function of the history of the control element. Since the aging of the control element is accelerated by high irradiating light intensities, the calibration may be carried out, for example, using a calibration parameter which is calibrated from the sum of the intensities that have previously fallen on the control element and been measured.

BRIEF DESCRIPTION OF THE DRAWING

Exemplary embodiments of the invention are shown in the drawing and are explained in greater detail in the following description.

FIG. 1 shows a device of the present invention in schematic representation;

FIG. 2 shows a variation of the device according to the invention;

FIG. 3 shows method steps of a method of the present invention in schematic representation;

FIG. 4 shows a further variation of a device according to the present invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a device of the present invention for the automatic control of illumination devices 24. It has a rain sensor 10 which is able to be calibrated by a calibration module 12.

Rain sensor 10 functions according to an optical total reflection method. A transmitter 14 sends light through a first light-conducting member 16 to a window 18, typically the windshield of a motor vehicle. The light penetrates window 18 and is totally reflected at the outside of window 18, facing away from first light-conducting member 16, at the glass-air interface, provided it is not wet from precipitation. The reflected light in turn travels from window 18 through first light-conducting member 16 to a receiver 20. This receiver 20 thereupon emits signals S, dependent on the light received, to calibration module 12.

To improve the ability to recognize precipitation on the outside of window 18, calibration module 12 performs a calibration in knowledge of the light emitted by transmitter 14.

Control element 22 is used for controlling illumination devices 24. The ambient light gets through window 18 and through second light-conducting member 26, arriving at a further receiver 28. It is connected to electronics 30 of control element 22 which evaluates its signals and, in dependence on them, controls illumination devices 24. To that end, stored in electronics 22 are so-called operating points which in each case correspond to a defined brightness. If the signal of further receiver 28 exceeds or falls below one or more of these operating points, illumination devices 24 are triggered, that is to say, are switched on or off or are dimmed.

First and second light-conducting members 16, 18 may naturally also be constructed in one piece. In the same way, electronics 30 of control element 22 may be disposed on the same board of calibration module 12, which may also fulfill still further functions.

FIG. 2 shows a variation of a device according to the present invention. In this case, no rain sensor is used for the calibration, but rather a separate calibration section within control element 22. Light from transmitter 14 is transmitted through light-conducting members 16, 26 to receiver 20. In knowledge of the transmitted and received light, electronics 30 thereupon performs a calibration. This alters the operating points stored in electronics 30, or amplifies the signal emitted by further receiver 28.

In the following, the functioning of the device of the present invention, and thus also the method of the present invention, are clarified.

In a first step 40, rain sensor 10 is activated. Using its transmitter 14, it thereupon sends light of predetermined intensity in the direction of window 18, and sees to it that window 18 is clean, i.e. is free of dirt and precipitation. This may be accomplished, for example, in that the rain sensor drives wiper motor M, and thus carries out a reference wiping using washer fluid, if desired.

In a calibration step 42, the light which was totally reflected at window 18 is detected by receiver 20. It thereupon emits a signal S to calibration module 12 of rain sensor 10, the calibration module then carrying out a comparison to a setpoint value which may also be transmitter-dependent. Since at this moment, window 18 is free of precipitation and dirt, signal S is determined primarily by the transparency of window 18 and of first light-conducting member 16, respectively. Because as a rule, window 18 in motor vehicles is made of laminated glass, signal S represents first and foremost a measure for the transparency of first light-conducting member 16. In this way, upon each activation or at other time intervals, which need be neither constant nor predetermined, rain sensor 10 is able to be calibrated.

Calibration parameters K obtained during this calibration step 42 are utilized in a third step 44 by control element 22 to shift the operating points at which, if they are exceeded or not attained, illumination devices 24 are triggered. If, for example, the result ascertained in calibration step 42 yields a transmission of 95 percentage of the setpoint value 100 percentage, then the operating points may be lowered by approximately 5 percentage in the result in order to compensate for the effect of second light conductor 26. Since first light-conducting member 16 and second light-conducting member 26 may also be made of different materials which may exhibit different aging behavior as well, electronics 30 of control element 22 may also carry out a correction of the result. This correction is stored as correlation in electronics 30, and may be made of a simple factor, or also of a complex function.

In a fourth step 46, the device is activated, so that if the operating points of control element 22 are exceeded or not attained, illumination devices 24 are triggered.

The ambient light travels through window 18 and second light-conducting member 26 to receiver 28. It relays further signals L, obtained therefrom, to electronics 30 which triggers illumination device 24 as a function of the operating points.

For example, the calibration process of control element 22 may be carried out upon each activation of rain sensor 10. Since the optical properties of the light conductor change only slowly, this is adequate, given sufficient frequency of precipitation. In principle, however, intervals I and T are completely independent, and therefore do not have to be either constant or identical. If control element 22 is not constantly active, rain sensor 10 may also store its last calibration parameter K, and upon activation of control element 22, may transmit it to it. The specific embodiment shown in FIG. 2 functions according to the same principle. Since here, however, the light from transmitter 14 does not have to be totally reflected at the outside of window 18, the need for the reference wiping in response to the activation is eliminated.

In one very simple design as shown in FIG. 4, the optical properties of light-conducting member 26 may also be determined approximately only from the service life. To that end, electronics 30 receives a time or date signal, and in accordance with it, with increasing age, shifts the operating points to a higher sensitivity. The magnitude of this shift may be determined, for example, from empirical values or model calculations.

In a variation, it is also conceivable to provide electronics 30 with a summator which totals the quantity of light fallen on light-conducting member 26 during the history of the control element. Typically, the properties of plastics, and consequently also their transmission properties, change due to exposure to sunlight. However, the light irradiation is continually measured by receiver 28, and in this way, conclusions may be drawn about the transmission properties of the light conductor. Using this data, the operating points may then be altered, and therefore a calibration may be carried out. A memory cell in combination with a capacitor may be used as summator, the memory cell being incremented when a defined voltage level is exceeded at the integrating capacitor, and it is thereupon discharged. In the simplest case, it is possible to use only a capacitor as summator.

In principle, a calibration of a control element for the automatic control of illumination devices 24 may also be achieved in that, at specific intervals, light of defined intensity and frequency is irradiated through windshield 18 and light-conducting member 26 onto further receiver 28, the signal emitted by further receiver 28 being used by electronics 30 for shifting the operating points. To that end, electronics 30 must be switched into a programming mode which, for example, may be achieved by a defined pulsed irradiation into receiver 28. This defined irradiation may be of a digital nature and correspond to a type of code. Therefore, the entire programming of control element 30 may be carried out on the basis of the incident light in further receiver 28, which means no further switching, trimming or connector elements are necessary on control element 30. If control element 30 has a plurality of receivers 28, then naturally the most varied combinations of lighting may also be used for the programming.

Of course, it is also possible to program the electronics of rain sensor 10 in this manner. 

What is claimed is:
 1. A method for automatically controlling at least one illumination device, comprising: acting on the at least one illumination device by a control element; calibrating the control element at first time intervals; for the first time intervals, accounting for calibration parameters by a rain sensor; calibrating the rain sensor at second time intervals; conducting light from a transmitter of the rain sensor via a first light-conducting member of the rain sensor into a receiver of the rain sensor; emitting by the receiver a plurality of signals as a function of the light received at the receiver; comparing a setpoint value to the plurality of signals; and calibrating the rain sensor as a function of a result of the comparing.
 2. The method as recited in claim 1, further comprising: determining a transmittance from the result of the comparing; and calibrating the control element in accordance with the transmittance.
 3. The method as recited in claim 2, wherein: the control element includes a second light-conducting member; optical properties of the second light-conducting member are in correlation with the transmittance; and the correlation is taken into account in the control element calibration.
 4. The method as recited in claim 3, wherein the correlation is stored as a functional cohesion in the control element.
 5. The method as recited in claim 3, wherein the correlation is stored as a table in the control element.
 6. The method as recited in claim 1, wherein the at least one illumination device is arranged in a motor vehicle.
 7. A device for automatically controlling at least one external illumination device, comprising: a rain sensor including a calibration module; and a control element for calibrating the device in accordance with at least one calibration parameter of the rain sensor; wherein the rain sensor includes: at least one transmitter for radiating light; a first light-conducting member; and a receiver which receives light from the at least one transmitter and emits transmission-dependent signals as a function of the light received, wherein the calibration module emits at least one result which is a function of a transmission of the first light-conducting member.
 8. The device as recited in claim 7, wherein the control element includes: a further receiver; and a second light-conducting member, wherein optical properties of the second light-conducting member are in correlation with the at least one result of the calibration module, wherein the control element accounts for the correlation in calibrating the device.
 9. The device as recited in claim 8, wherein the correlation is stored in the control element as a functional cohesion.
 10. The device as recited in claim 8, wherein the correlation is stored in the control element as a cohesion in table form.
 11. The device as recited in claim 8, wherein the first light-conducting member and the second light-conducting member are constructed in one piece.
 12. The device as recited in claim 7, wherein: the rain sensor includes a first electronics; and the control element includes a second electronics, the first electronics and the second electronics arranged in one piece.
 13. The device as recited in claim 12, wherein the one piece is arranged on a board. 